Actually these were polyester mesh. We did use the stainless mesh for some items. It was tricky to stretch in a frame.
The 300 was our standard mesh and we used a 350 or 400 for printing images that had reverse type in them to reduce the bleed into the type, we did some very small items.
Heres one place that carries that mesh.
Looking at that glass plate you coated it's evident you have a contamination issue with the ripples and holes. How did you clean the glass prior to coating, anything that would leave a residue?